JPH06202060A - LCD display panel inspection device - Google Patents

Abstract

(57) [Abstract] [Purpose] To realize an inspection device capable of uniformly measuring the liquid crystal display panel for display quality defects such as unevenness, black spots, and white spots, regardless of the viewing angle. A light source device 5 is disposed below the panel 1 to be inspected, a light diffusion plate 6 is disposed between the light source device 5 and the panel 1 to be inspected, and a concave mirror 3 is disposed above the panel 1 to be inspected. The CCD camera 2 and the slit plate 4 are provided in front of the CCD camera 2 on the optical path of the reflected light. The concave mirror 3 is arranged so that its lens axis forms an angle of 45 ° with the horizontal direction. The light emitted from the light source device 5 and passing through the panel 1 to be inspected vertically from below is bent by 90 ° by the concave mirror 3 to take an optical path in the horizontal direction. Of these lights, only parallel rays pass through the slit at the center of the optical axis, and the rays other than parallel rays are shielded by the slit plate 4,
Only parallel rays reach the camera 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display panel inspection device for checking the display quality of a liquid crystal display panel.

[0002]

2. Description of the Related Art As liquid crystal display panels, TN type, ST type
N-type liquid crystal display panels are frequently used, but as display quality defects of this type of liquid crystal display panel, there are, for example, unevenness, black spots, white spots, and the like. Although these defective elements are not a serious problem in a small liquid crystal display panel used in a wristwatch or the like, they are magnified and easily noticeable in a large liquid crystal display panel, so that the commercial value thereof is significantly reduced. Therefore, in the manufacturing process, it is necessary to strictly check such a display quality defect and, if it is defective, correct it.

As an inspection method for this display defect,
Conventionally, this has been done by the visual inspection of an inspector. However, since visual inspection requires skill, there is a drawback that uniform inspection cannot be performed.

As a method of optically detecting the above-mentioned display quality defect in order to make up for such a drawback of the manual visual inspection, there is a method shown in FIG. 3, for example. In this method, an image of the display screen of the liquid crystal display panel 1 is picked up by a detecting image pickup device 2 (CCD camera) using an image pickup tube, a CCD device, a Cds device, or the like, and then an image pickup signal is processed by a signal processing circuit 11. The output signal is arithmetically processed by the arithmetic processing circuit 12, and the quality of the display quality is determined based on the arithmetic result.

[0005]

By the way, TN type, S type
A liquid crystal display panel such as a TN type displays an image by utilizing the birefringence of liquid crystal, and therefore, depending on whether the line of sight is vertical to the panel or tilted vertically or horizontally. The display contrast differs depending on the tilt angle.

That is, as shown in FIGS. 4 and 5,
For example, the line of sight is perpendicular to the liquid crystal display panel (= 0.
When the display contrast ratio is shifted downward by 14 ° from 0 °), as is understood from FIG.
It has dropped significantly from 50 to 30. In addition, also in FIG. 5, the line of sight is in the direction perpendicular to the liquid crystal display panel (= 0.
It is understood that the contrast ratio is significantly reduced from 200 to 30 when the angle is shifted 30 ° to the right from (°).

This is because the anisotropy of the refractive index and the distance that light traverses the liquid crystal layer differ depending on the viewing angle. For example, in a normally white liquid crystal display panel, when a voltage is applied to the liquid crystal to display it in black, or when the line of sight is tilted in the vertical direction or tilted in the horizontal direction, the light is transmitted without being shielded. Incident light leakage increases. When a person looks at it, he or she can recognize the display quality itself such as unevenness, black spots, white spots, etc. without being confused by the contrast difference when tilted in the vertical and horizontal directions. When measured by the above method, the contrast difference data and the display unevenness data on the panel cannot be discriminated from each other, which may lead to erroneous determination.

Therefore, conventionally, the following measures have been taken.

A large distance is set to reduce the angle difference.

The measurement area is divided into minute areas for measurement.

The difference in the contrast ratio is assumed in advance, and the calculation process is performed by adding the correction amount according to the difference in the ratio.

However, in the above method, although there is no problem with a relatively small panel, a large liquid crystal display panel has a problem that a difference in contrast ratio begins to appear even when the viewing angle is about ± 5 °. Therefore, it is necessary to secure a sufficient distance, but for this purpose, even a panel with a diagonal of 10 inches will be measured from a distance of at least 2 to 3 m or more, and the device becomes very large, which is not practical. .

In addition, the device which has taken the above measures has a problem that a large-scale arithmetic unit is required in terms of a system. Another problem is whether the assumed contrast difference and the actual contrast difference match each liquid crystal display panel and whether the result can be trusted.

For these reasons, in the conventional optical inspection described above, it is not possible to carry out an accurate display quality inspection with a small device configuration due to the influence of the viewing angle.

The present invention has been made in order to solve the above problems, and an inspection can be performed with high accuracy and a simple system configuration for detecting display unevenness of a liquid crystal display panel panel without depending on a viewing angle. The purpose is to provide a device.

[0016]

A liquid crystal display panel inspection apparatus according to the present invention comprises a light source for irradiating the liquid crystal display panel with light.
Condensing means for condensing the light transmitted through the liquid crystal display panel or the light reflected from the liquid crystal display panel, and out of the light condensed by the condensing means, the parallel light before condensing is taken out, A liquid crystal display panel inspection device comprising: a means for guiding the parallel light to a light receiving means; and a determination means for determining the quality of the display quality of the liquid crystal display panel based on a detection signal from the light receiving means. To be achieved.

Further, it is preferable to use a diaphragm as a means for guiding the parallel light to the light receiving means.

Further, it is preferable to use a concave mirror as the light converging means.

Further, it is preferable to use a convex lens for the light converging means.

[0020]

According to the structure of the present invention, of the light emitted from the liquid crystal display panel, only the parallel light before condensing reaches the light receiving means and is coupled onto the light receiving element of the light receiving means. That is, since all the pixels of the liquid crystal panel are directly faced and received by the light receiving elements in a one-to-one correspondence, an accurate inspection can be performed.

[0021]

【Example】

Example 1 An example of the present invention will be described below. First Embodiment FIG. 1 shows a liquid crystal display panel inspection apparatus according to a first embodiment of the present invention. This inspection apparatus includes a light source device 5 arranged below a liquid crystal display panel to be inspected (hereinafter referred to as an inspected panel 1), and a light diffusion plate disposed between the light source device 5 and the inspected panel 1. 6, a concave mirror 3 arranged above the panel 1 to be inspected, a CCD camera 2 arranged on the optical path of the reflected light L ₂ from the concave mirror 3, and a slit at the center of the optical axis in front of the CCD camera 2. And the slit plate 4 arranged at the focal position of the concave mirror 3. As the CCD camera 2, in the present embodiment, a video CCD camera having a built-in 1/2 inch CCD element was used. A hot cathode tube was used as the light source device 5. The light diffusion plate 6 is for making the illuminance uniform over the entire plane of the panel 1 to be inspected. The concave mirror 3 has a focal length of 300 mm, and is arranged vertically above the panel 1 to be inspected 300 mm so that its lens axis forms an angle of 45 ° with the horizontal direction.

The panel 1 to be inspected has a diagonal dimension of 10 inches and each pixel dimension is 0.33 mm × 0.11 m.
A color display TN type liquid crystal display panel with m and the number of picture elements 640 × 480 × 3 = 921,600 was used. Although the polarizing plate integrated with the panel 1 to be inspected is used, the polarizing plate and the panel 1 to be inspected may be separately placed and arranged before and after the panel 1 to be inspected.

In addition, this inspection apparatus has a signal processing circuit 11 and an arithmetic processing circuit 12 connected to the CCD camera 2.

Illumination light L ₁ emitted from the light source device 5 is transmitted through the panel 1 to be inspected while the illuminance is made uniform by the light diffusing plate 6, and then is reflected by the concave mirror 3 to bend the optical path by 90 °. And take the optical path in the horizontal direction. Of the reflected light L ₂ , only parallel rays pass through the slit at the center of the optical axis, and light other than parallel rays is blocked by this slit plate 4. Therefore, only parallel rays are guided to the CCD camera 2.

With such a configuration, as shown in FIG. 1, a virtual image of the panel 1 to be inspected is formed at a position opposite to the CCD camera 2 with the concave mirror 3 interposed therebetween, and the virtual image is reduced to C.
The image is taken by the CD camera 2. Therefore, the pixels of the panel 1 to be inspected face the individual image pickup element of the CCD camera 2,
And one-to-one is imaged.

Then, the output from the CCD camera 2 is input to the signal processing circuit 11, where predetermined signal processing is performed and input to the arithmetic processing circuit 12.

Data in the case where the display quality of the liquid crystal display panel is non-defective is input in advance to the arithmetic processing circuit 12, and this data is compared with the image data of the panel 1 to be inspected given from the signal processing circuit 11. And the panel to be inspected 1
It is determined whether or not there are display quality defects such as unevenness, black spots, and white spots, and the quality of the panel 1 to be inspected is determined. Here, the defective product is returned to the correction process together with the type of defect and the data of the defective signal, and the non-defective product is transported to the next process.

(Embodiment 2) FIG. 2 shows a panel inspection apparatus according to Embodiment 2 of the present invention. In the second embodiment, the convex lens 7 is arranged between the panel 1 to be inspected and the slit plate 4,
The convex lens 7 collects the light transmitted through the panel 1 to be inspected. The CCD camera 2 is provided behind the slit plate 4 which has a slit at the center of the optical axis and is provided at the focal position of the convex lens 7.
Is arranged, and after being condensed by the convex lens 7, only the parallel light before being condensed is received by the CCD camera 2 through the slit plate 4. Thereafter, the same signal processing and arithmetic processing as those in the first embodiment are performed to determine the quality of the inspected panel 1. The second embodiment has the advantages that the convex lens 7 is inexpensive and the optical system can be easily assembled.

[0029]

As described above, according to the liquid crystal display panel inspection apparatus of the present invention, of the light emitted from the inspection panel, only the parallel light before passing through the diaphragm means reaches the light receiving means, and the light receiving means receives light. Tied on the element. That is, since all the pixels of the liquid crystal panel are face-to-face and are received by the light-receiving element in a one-to-one correspondence, it is not necessary to correct the data. Therefore, an accurate inspection can be performed over the entire screen of the liquid crystal panel without depending on the viewing angle with respect to the liquid crystal panel.

Further, according to the liquid crystal display panel inspection apparatus of the third aspect, since the convex lens is used as the light converging means,
It is inexpensive and easy to install.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a first embodiment of a liquid crystal display panel inspection device of the present invention.

FIG. 2 is a schematic diagram showing a second embodiment of the liquid crystal display panel inspection device of the present invention.

FIG. 3 is a graph showing changes in contrast ratio when the field of view is tilted in the vertical direction.

FIG. 4 is a graph showing changes in contrast ratio when the field of view is tilted in the left-right direction.

FIG. 5 is a schematic diagram showing a liquid crystal display panel inspection device according to a conventional example.

[Explanation of symbols]

1 panel to be inspected 2 CCD camera 3 concave mirror 4 slit plate 5 light source device 6 light diffusing plate 7 convex lens 11 signal processing circuit 12 arithmetic processing circuit L ₁ illumination light L ₂ reflected light

Claims (4)

[Claims] 1. A light source for irradiating a liquid crystal display panel with light, a light condensing means for condensing light transmitted through the liquid crystal display panel or light reflected from the liquid crystal display panel, and light condensing means for condensing the light. A means for extracting parallel light before condensing out of the collected light and guiding the parallel light to a light receiving means, and a judgment means for judging the quality of the display quality of the liquid crystal display panel by a detection signal of the light receiving means. Liquid crystal display panel inspection device having a. 2. The liquid crystal display panel inspection device according to claim 1, wherein a diaphragm is used as a means for guiding the parallel light to the light receiving means. 3. The liquid crystal display panel inspection device according to claim 1, wherein a concave mirror is used as the light converging means. 4. A convex lens is used as the light converging means.
The liquid crystal display panel inspection device according to 1.